During the spin cycle of a washing machine, water is removed from wet clothes centrifugally by spinning the clothes at high speed in a spin basket. In order to reduce the possibility of injury to the user, the user must be prevented from having access to the spin basket while the spin basket is in motion either during the spin or agitate cycle.
One way of protecting the user from access to the rotating spin basket uses an electrically locking latch for the washing machine lid. The latch holds and locks the lid in a closed position for the duration of the spin cycle and for a period after the spin cycle necessary for the spin basket to coast to a stop. This locking latch may be operated by a thermoelectric element such as a bimetallic strip or wax motor. Preferably, however, a fast acting solenoid or an electrical motor may be used for the locking mechanism to permit rapid access to the clothes when the spin basket has stopped. The electrical motor or a bi-stable solenoid may receive a first polarity pulse of electricity to lock the lid and a second polarity pulse of electricity to unlock the lid, thereby saving electrical power in the steady-state.
In order to prevent defeat of the lock, it is known to put a lid switch in series with the electrical actuator to prevent the locking action when the lid is open. This lid switch may be accompanied with a “lock switch” indicating that the bolt of the lock is engaged with a door strike. The lock switch is then placed in series with the washing machine motor or tied to the washing machine controller to prevent activation of the spin cycle when the lid is not properly locked. Together the lid closure switch and the lid lock switch provide some assurance that the lid is properly closed and locked before power is applied to the washing machine mechanism.
More recently, improved prevention of lock tampering has been provided by providing separate switches that detect both a locked state and an unlocked state of the lock. The separate switches provide the ability to detect a jamming of the lock mechanism preventing full movement of the lock mechanism between locked and unlocked states, such as may also indicate tampering or damage to the lock.
These additional switches require separate independent electrical conductors leading between the lock mechanism and the appliance control increasing the cost of the wiring harness and the complexity of manufacturing.